Plant responses to abiotic stress: the chromatin context of transcriptional regulation

The ability of plants to cope with abiotic environmental stresses such as drought, salinity, heat, cold or flooding relies on flexible mechanisms for re-programming gene expression. Over recent years it has become apparent that transcriptional regulation needs to be understood within its structural context. Chromatin, the assembly of DNA with histone proteins, generates a local higher-order structure that impacts on the accessibility and effectiveness of the transcriptional machinery, as well as providing a hub for multiple protein interactions. Several studies have shown that chromatin features such as histone variants and post-translational histone modifications are altered by environmental stress, and they could therefore be primary stress targets that initiate transcriptional stress responses. Alternatively, they could act downstream of stress-induced transcription factors as an integral part of transcriptional activity. A few experimental studies have addressed this ‘chicken-and-egg’ problem in plants and other systems, but to date the causal relationship between dynamic chromatin changes and transcriptional responses under stress is still unclear. In this review we have collated the existing information on concurrent epigenetic and transcriptional responses of plants to abiotic stress, and we have assessed the evidence using a simple theoretical framework of causality scenarios

Light and temperature shape nuclear architecture and gene expression

Environmental stimuli play a major role in modulating growth and development throughout the life-cycle of a plant. Quantitative and qualitative variations in light and temperature trigger changes in gene expression that ultimately shape plant morphology for adaptation and survival. Although the phenotypic and transcriptomic basis of plant responses to the constantly changing environment have been examined for decades, the relationship between global changes in nuclear architecture and adaption to environmental stimuli is just being uncovered. This review presents recent discoveries investigating how changes in light and temperature trigger changes in chromatin structure and nuclear organization with a focus on the role of gene repositioning and chromatin accessibility in regulating gene expression

The impact of light and temperature on chromatin organisation and plant adaptation

Light and temperature shape the developmental trajectory and morphology of plants. Changes in chromatin organisation and nuclear architecture can modulate gene expression and lead to short and long-term plant adaptation to the environment. Here, we review recent reports investigating how changes in chromatin composition, structure and topology modulate gene expression in response to fluctuating light and temperature conditions resulting in developmental and physiological responses. Furthermore, the potential application of novel revolutionary techniques such as RNA and padlock fluorescence in situ hybridization (FISH), and Hi-C to study the impact of environmental stimuli such as light and temperature on nuclear compartmentalisation in plants is discussed

The Histone Deacetylase Complex (HDC) 1 protein of Arabidopsis thaliana has the capacity to interact with multiple proteins including histone 3-binding proteins and histone 1 variants

Intrinsically disordered proteins can adopt multiple conformations thereby enabling interaction with a wide variety of partners. They often serve as hubs in protein interaction networks. We have previously shown that the Histone Deacetylase Complex (HDC) 1 protein from Arabidopsis thaliana interacts with histone deacetylases and quantitatively determines histone acetylation levels, transcriptional activity and several phenotypes, including ABA-sensitivity during germination, vegetative growth rate and flowering time. HDC1-type proteins are ubiquitous in plants but they contain no known structural or functional domains. Here we explored the protein interaction spectrum of HDC1. In addition to binding histone deacetylases, HDC1 directly interacted with core histone H3-binding proteins and co-repressor associated proteins, but not with H3 or the co-repressors themselves. Surprisingly, HDC1 was also able to interact with variants of the linker histone H1. Truncation of HDC1 to the ancestral core sequence narrowed the spectrum of interactions and of phenotypic outputs but maintained binding to a H3-binding protein and to H1. The results indicate a potential link between H1 and histone modifying complexes

The diverse and unanticipated roles of Histone deacetylase 9 in coordinating plant development and environmental acclimation

Plants tightly control gene transcription to adapt to environmental conditions and steer growth and development. Different types of epigenetic modifications are instrumental in this. In recent years, an important role for the chromatin modifying RPD3/HDA1 class I HDAC HISTONE DEACETYLASE 9 (HDA9) emerged in the regulation of a multitude of plant traits and responses. HDACs are widely considered transcriptional repressors and are typically part of multiprotein complexes containing co-repressors, DNA and histone binding proteins. By catalyzing the removal of acetyl groups from lysine residues of histone protein tails, HDA9 indeed negatively controls gene expression in many cases, in concert with interacting proteins such as POWERDRESS (PWR), HIGH EXPRESSION OF OSMOTICALLY RESPONSIVE GENES 15 (HOS15), WRKY53, ELONGATED HYPOCOTYL 5 (HY5), ABA INSENSITIVE 4 (ABI4) and EARLY FLOWERING 3 (ELF3). However, HDA9 activity has also been directly linked to transcriptional activation. In addition, following the recent breakthrough discovery of mutual negative feedback regulation between HDA9 and its interacting WRKY-domain transcription factor WRKY53, swift progress in gaining understanding of HDA9 biology is expected. In this review, we summarize knowledge on this intriguing versatile – and long underrated – protein and propose novel leads to further unravel HDA9-governed molecular networks underlying plant development and environmental biology

Metacognition, Borderline Pathology and Psychotherapeutic Change: A Single-Case Study

The aim of this study is to analyze whether: (a) a specific type of metacognitive deficit is present in a patient with Borderline Personality Disorder; (b) a metacognitive improvement can be detected during the psychotherapy treatment; (c) if this improvement can be indicative of the effectiveness of psychotherapy itself. A single case study has been conducted; metacognitive deficits have been measured with the Metacognition Assessment Scale (MAS). In line with the hypothesis, the results show a global and progressive improvement of meta-cognitive functions. We conclude in agreement with the current literature, the existence of a major deficit in Differentiation and Integration subfunctions (belonging to Self-reflexivity), compared to Characterization and Relation between variables subfunctions (belonging to Metacognitive monitoring)

Let it bloom: crosstalk between light and flowering signalling in Arabidopsis

The terrestrial environment is complex, with many parameters fluctuating on daily and seasonal basis. Plants in particular, have developed complex sensory and signalling networks to extract and integrate information about their surroundings, in order to maximise their fitness and mitigate some of the detrimental effects of their sessile lifestyles. Light and temperature each provide crucial insight on the surrounding environment and in combination allow plants to appropriately develop, grow and adapt. Crosstalk between light and temperature signalling cascades allow plants to time key developmental decisions accordingly to ensure they are “in sync” with their environment. In this review, we discuss the major players that regulate light and temperature signalling, and the cross‐talk between them, in reference to a crucial developmental decision faced by plants: to bloom or not to bloom

ZINC-FINGER interactions mediate transcriptional regulation of hypocotyl growth in Arabidopsis

Integration of environmental signals and interactions among photoreceptors and transcriptional regulators is key in shaping plant development. TANDEM ZINC-FINGER PLUS3 (TZP) is an integrator of light and photoperiodic signaling that promotes flowering in Arabidopsis thaliana. Here we elucidate the molecular role of TZP as a positive regulator of hypocotyl elongation. We identify an interacting partner for TZP, the transcription factor ZINC-FINGER HOMEODOMAIN 10 (ZFHD10), and characterize its function in coregulating the expression of blue-light–dependent transcriptional regulators and growth-promoting genes. By employing a genome-wide approach, we reveal that ZFHD10 and TZP coassociate with promoter targets enriched in light-regulated elements. Furthermore, using a targeted approach, we show that ZFHD10 recruits TZP to the promoters of key coregulated genes. Our findings not only unveil the mechanism of TZP action in promoting hypocotyl elongation at the transcriptional level but also assign a function to an uncharacterized member of the ZFHD transcription factor family in promoting plant growth

ERRATUM: Metacognition, borderline pathology and psychotherapeutic change: a single-case study

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Working Memory abilities, attachment relationships and learning process in children of primary school age: an empirical research

Several studies underline a definite link between “working memory†(WM) and the learning process (deficit and learning disorder in children). WM abi-lities mainly affect written language learning and arithmetic learning. According to studies related to the Attachment Theory, it is possible to rationalize that child with a secure attachment to the caregiver and/or to the teacher have higher skills in school adaptability. In this study—based on previous pilot study (Del Villano, Ce-cere, Sapuppo, & Caviglia., 2011)—the relationship between: cognitive test (WM measurement test), learning test and the student’s attachment style (both with his caregivers and his teacher) have been empirically evaluated. This pilot study was performed in several of the primary schools in Campania Italy between 2009 and 2011. The selected sample was composed of 80 children 6-7 years old (38 Female and 42 Male) who, after parental and school consent, were tested by the tools de-scribed in the main body of this research paper. The pilot study shows an absence of linguistic deficit, and a relationship between cognitive abilities and the learning le-vel achieved in reading and mathematical calculation, furthermore it has shown a modulation effect of the attachment on the relationship between the WM ability and MT calculation and reading tests. This modulation effect is more evident if we consider the unsecure or disorganized attachment, especially if we consider the data accumulated with reference to the attachment to the teacher. Our research was conducted with the sole intention to widen the sample and make the outcomes more valid and reliable. The recruited sample was composed of 130 children age 6-7 who, after parenentalt and school consent, were tested with the TVL -Linguistic As-sessment Test , the short version of AWMA (Automated Working Memory As-sessment), the SAT-Separation Anxiety Test, both family and school versions, and the Reading Trials MT -AC-MT 6-11- Calculation Ability Assessment Test. The re-sults underline the absence of deficit or malfunctions in the subjects’ linguistic de-velopment, a significant connection between the learning performances and the verbal and visual-spatial trials assessed with the AWMA, and a moderating effect of the attachment style upon the connection itself